From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754000AbbIGIUd (ORCPT ); Mon, 7 Sep 2015 04:20:33 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:5764 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753093AbbIGIUa (ORCPT ); Mon, 7 Sep 2015 04:20:30 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Mon, 07 Sep 2015 01:16:04 -0700 Date: Mon, 7 Sep 2015 10:20:18 +0200 From: Thierry Reding To: Yakir Yang CC: Russell King , Rob Herring , Heiko Stuebner , Jingoo Han , Inki Dae , Joe Perches , Kukjin Kim , Krzysztof Kozlowski , Mark Yao , , , , Ajay kumar , Andrzej Hajda , Kyungmin Park , David Airlie , Gustavo Padovan , Andy Yan , Kumar Gala , Ian Campbell , Rob Herring , Pawel Moll , Kishon Vijay Abraham I , , dri-devel , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-samsung-soc@vger.kernel.org" , , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v4 14/16] drm: bridge: analogix/dp: try force hpd after plug in lookup failed Message-ID: <20150907082017.GB19961@ulmo.nvidia.com> References: <1441086371-24838-1-git-send-email-ykk@rock-chips.com> <1441088079-25809-1-git-send-email-ykk@rock-chips.com> <55E7CC43.7040608@rock-chips.com> <20150903090421.GC3784@ulmo.nvidia.com> <55EBBA0C.1030100@rock-chips.com> MIME-Version: 1.0 In-Reply-To: <55EBBA0C.1030100@rock-chips.com> X-NVConfidentiality: public User-Agent: Mutt/1.5.23+102 (2ca89bed6448) (2014-03-12) X-Originating-IP: [10.2.71.38] X-ClientProxiedBy: UKMAIL101.nvidia.com (10.26.138.13) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ftEhullJWpWg/VHq" Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ftEhullJWpWg/VHq Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Sep 06, 2015 at 11:59:08AM +0800, Yakir Yang wrote: > Hi Thierry, >=20 > =E5=9C=A8 09/03/2015 05:04 PM, Thierry Reding =E5=86=99=E9=81=93: > >On Thu, Sep 03, 2015 at 12:27:47PM +0800, Yakir Yang wrote: > >>Hi Rob, > >> > >>=E5=9C=A8 09/03/2015 04:17 AM, Rob Herring =E5=86=99=E9=81=93: > >>>On Tue, Sep 1, 2015 at 1:14 AM, Yakir Yang wrote: > >>>>Some edp screen do not have hpd signal, so we can't just return > >>>>failed when hpd plug in detect failed. > >>>This is a property of the panel (or connector perhaps), so this > >>>property should be located there. At least, it is a common issue and > >>>not specific to this chip. We could have an HDMI connector and failed > >>>to hook up HPD for example. A connector node is also where hpd-gpios > >>>should be located instead (and are already defined by > >>>../bindings/video/hdmi-connector.txt). Perhaps we need a eDP connector > >>>binding, too. > >>Yep, I agree with your front point, it is a property of panel, not spec= ific > >>to eDP controller, so this code should handle in connector logic. > > From your description it sounds more like this is in fact a property of > >the panel. Or maybe I should say "quirk". If the panel doesn't generate > >the HPD signal, then that should be a property of the panel, not the > >connector. The eDP specification mandates that connectors have a HPD > >signal, though it allows the "HPD conductor in the connector cable" to > >be omitted if not used by the source. I'd consider the cable to belong > >to the panel rather than the connector, so absence of HPD, either > >because the cable doesn't have the conductor or because the panel does > >not generate the signal, should be a quirk of the panel. > > > >That said you could have a panel that supports HPD connected via a cable > >that doesn't transmit it, so this would be a per-board variant and hence > >should be a device tree property rather than hard-coded in some panel > >driver. > > > >Conversely, if the panel isn't capable of generating an HPD signal, then > >I don't think it would be appropriate to make it a DT property. It would > >be better to hard-code it in the driver, lest someone forget to set the > >property in DT and get stuck with a device that isn't operational. >=20 > Oh, you're right, if it's a cable quirk, then DT property would be okay, = if > it > is a problem of panel, then maybe hard-code in driver would be better. >=20 > After look up for the document of panel "innolux,n116bge", I haven't see > any description of hot plug signal, and even not found in PIN ASSIGNMENT. > So I believe it's a panel problem, that's to say it should handle in panel > driver. The datasheet that I have for that panel lists HPD as pin 17. Also I used to have a setup with that panel and I distinctly remember hotplug working just fine. Perhaps this is an issue with a specific variant of the panel? Or perhaps this is indeed a problem with the cable that's connecting the panel to the board. It could be one of those cases where they left out the HPD conductor to save money. Thierry --ftEhullJWpWg/VHq Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAABCAAGBQJV7UjBAAoJEN0jrNd/PrOhE68P/0B1Ca2qOrOsr1K0KU/AQhsk DwpfyUV93vVdsTaSVyinlXsMi+Dpr3kse6y94kvLudF5r0yqMVcIHEuGwq5GkVAC R2KexsvfBCtdIh2vF8C2zwSwpRJBmk42kWPzgcI+/Jbal4LKSoOvn3GJhalwWMxK zfMhsjgb2XWFQPn7rdlHQ08z8v2ZV3njHPz/SF6aaKh5L6WZTFGRRifQcBzTzJh6 dDZ1T+MTjcDbEjOtTThhhS9976OM9NalebudYT/VQ1HZtOTCJu4s+fX2S9fltSVk 4TFIjgs1KXOCRB0knP6ITYOaHAZoydOnoJo/FCQClj4tiWuf4g42/lukW3oeYr3/ fNYOqfncKtSdvavtQCUUra/PvrygiZya8AvcGRVqZub/vmyqmTmPSmS4UKOr6i+j lzfuoP0ubWe3gjFdJafa4kbWHd15j9+PxXKAgxhkUVt7UsWAejSQMnM4scLqy9dJ HwwlxL8umkt1cMng4YmAIz4EIYI4P/Uu8cA+w+RtzzK7GVNOlrudtM5PrubjU33G DvLTucz82biGx9B+SlTjEsYFKWPeimhwEkvzXauHmDp4AHwjS9d1I245f2FmJfLd bJ9i/DvHwxJ9PbdLFl7P9m1kVhc9dp6MuKb4Vkm92UPmU7X9m6ls7o+uSLWN6vx2 /OgBPesp9l+CXunS2aL9 =DkJC -----END PGP SIGNATURE----- --ftEhullJWpWg/VHq--